Angled examination mirrors are commonly used by dentists during examination, prophylaxis and treatment. It has long been known that such a mirror tends to accumulate condensation when it is placed in a patient's mouth if the mirror is significantly colder before insertion than the temperature of the mouth. This tendency, known as fogging, is a nuisance to the dentist and the patient because it obscures the dentist's vision and requires that the mirror surface be wiped clean rather frequently, thereby delaying or extending the examination or treatment process. It can also be somewhat more serious than a mere nuisance if the dentist is at a critical point in a treatment procedure, and suddenly finds that he cannot properly see the subject of his efforts.
Repeated wiping of the mirror surface to remove the fog is therefore a necessity and is not only annoying, distracting and time consuming but can also represent a condition of reduced sanitation.
A readily apparent solution to the problem is to elevate the temperature of the mirror to about body temperature or slightly above. While this is, in theory, a successful solution, there has been no fully satisfactory device developed to quickly and adequately heat the mirror to the desired temperature without excessive use of energy, overheating, or excessive cost. Examples of prior art devices designed to accomplish heating of dental mirrors or heating or drying of other small devices are found in the following U.S. Patents.
Monnont (U.S. Pat. No. 2,471,884) shows a standard dentist's instrument tray which has heating elements beneath the tray to elevate its temperature so that any instrument placed thereon will be heated.
De Terra (U.S. Pat. No. 1,843,067) shows a dental mirror with a heat storage fluid to retain heat after holding the mirror in a flame.
Dreher (U.S. Pat. No. 2,625,858) shows a dental mirror with a heat conductive handle to convey body heat to the mirror.
Goodsell et al (U.S. Pat. No. 281,224), Bennett et al (U.S. Pat. No. 709,812), Wilson (U.S. Pat. No. 1,934,110) and Densten (U.S. Pat. No. 2,120,091) show dental mirrors with electric heating elements therein attached by wires to a power source.
The following patents show cabinets of various kinds for heating or sterilizing diverse items such as toothbrushes or medical implements using hot air, a heating lamp or some other form of heating means.
______________________________________ Re. 24,738 Kueser 1,824,310 Thompson 2,180,213 Peake 2,616,269 Reynolds 2,999,145 Espenhain 3,278,256 Skaller 3,353,905 Ellis 3,637,982 Reaves 3,776,694 Leittl 3,820,251 Abernathy 3,961,893 Russell et al. ______________________________________
As will be seen, some previously developed solutions involve the connection of electrical power directly to the mirror. While this may adequately heat the mirror, the existence of wires to the mirror handle adds to the mirror weight and severely restricts the dentist's freedom of manipulation of the mirror, an important need. Other devices using heating elements in an instrument tray, light bulbs, and the like are quite wasteful of energy and do not provide any technique for exercising control over the ultimate temperature of the mirror or handle with the result that the mirror may not be sufficiently warmed or may be overheated to the discomfort of the patient or the dentist.